Gloves fabricated from elastomeric materials such as natural rubber latex and synthetic latex have encountered a variety of problems. An important criterion for medical gloves is that they conform tightly to the hand of the wearer. Natural rubber, with its inherent high coefficient of friction, makes glove donning difficult. To solve this problem, conventional medical gloves use a lubricant on the inner surface to ease glove donning. This lubricant also serves to ease removal of the glove from the hand-shaped former used in manufacturing. Commonly, the lubricant is in powder form and is generally of an absorbent nature; for example, starch powder is commonly used. There have, however, been doubts in the medical community about using loose dusting powder in gloves used for surgical procedures. As a result, many efforts have been made to reduce or eliminate the use of loose powder to facilitate the donning of medical gloves by developing various powder-free methods to improve donning properties.
Synthetic latex and natural rubber gloves are commonly fabricated by a process of first dipping a hand-shaped former, or mandrel, into a powdered coagulant bath, dipping the former into a latex or natural rubber bath, and finishing with a leaching and drying process. Frequently, gloves made by this process result in gloves that have a tendency to stick to the former after drying. Upon stripping the glove from the former, gloves fabricated by this process often tear and stick together.
In commercially made gloves, the coagulant bath includes a powder of mineral origin to provide antiblocking properties on the former surface. Antiblocking powders prevent the two layers of the glove from sticking to one another. The powder is usually calcium carbonate or talc, as these powders can withstand the high temperatures (100-130° C.) used in latex glove fabrication. On the outside surface, a starch or other powder layer is applied by dipping a former with a cured latex glove into a starch slurry bath. Alternatively, the cured latex glove may be coated with a synthetic polymer coating to impart antiblocking properties.
There are also disclosures relating to off-line chlorination, washing and siliconization processes for making powder-free medical gloves. These processes remove talc and cornstarch powder residues, reduce tackiness and improve glove donnability. These processes, however, are usually labor-intensive and use large amounts of water, making them very expensive. Moreover, chlorination can result in poor physical strength, discoloration and poor aging characteristics of the glove. In some situations, chlorination can pose storage and environmental hazards.
The making of powder-free medical gloves using a chlorination process, polymer coating methods, or a combination of both, are disclosed in U.S. Pat. Nos. 6,195,805; 5,674,818; 5,612,083; 5,570,475; 5,284,607; 5,088,125; 4,597,108 and 4,143,109. There are, however, few disclosures describing the malting of powder-free gloves without post-processing, or off-line, steps such as chlorination, washing and/or siliconization. Among these few disclosures are U.S. Pat. Nos. 6,075,081; 5,534,350 and 4,310,928.
U.S. Pat. No. 6,075,081 to Nile discloses a powder-free coagulant for use in latex dipping processes comprising a salt-stable dispersion of a polychloroprene rubber and an inorganic metal salt. The coagulant of this disclosure may also contain a powder-free release agent comprising a polypropylene wax emulsion and a cationic surfactant to aid release of the dipped article from the former.
U.S. Pat. No. 5,534,350 to Liou discloses an on-line process of making powder-free medical gloves using a polyurethane polymer in the coagulant that acts as a waterproof lubricating layer to ease stripping the glove from the ceramic former. A coat of polyurethane polymer on the inside of the glove improves donning.
U.S. Pat. No. 4,310,928 to Joung discloses coating a glove former with a coagulant containing a lipo compound and a surfactant in a dispersion. These materials stay with the glove after it is stripped from the former, thereby providing a release surface for the glove.
Additionally, U.S. Pat. No. 6,378,137 to Hassan et al. discloses the making of a powder-free medical glove that uses an antiblocking composition of a polymer or copolymer mixed with a micronized high-density polyethylene material and a wax. This composition makes the glove easier to don. However, the glove remains only substantially free of powder in the finished product and requires treatment with a silicone emulsion/wax mixture in off-line processing. U.S. Pat. No. 6,019,922 to Hassan et al. discloses an additional method for making powder-free medical gloves that includes a silicone treatment on the outside surface of the glove and an antiblocking composition on the inside surface of the glove. The antiblocking composition of this reference is comprised of a polymer or copolymer, a micronized high-density polyethylene material and wax. To manufacture the gloves of this reference, however, the manufacturer must rinse the finished glove to remove remaining coagulant powder. This rinsing process is not perfected and results in gloves that are only substantially free of powder, rather than completely free of powder. The glove process of this disclosure also requires off-line processing, including treatment of the gloves with a silicone solution to produce a finished product.
It is therefore desirable to have a powder-free, non-tacky glove with good donning properties that can be easily stripped from a glove former following fabrication. It is also desirable that this powder-free glove require only a minimal number of processing steps, most preferably requiring no off-line processing. It is therefore desirable to provide a novel way of producing powder-free synthetic latex or natural rubber dipped gloves that solves the foregoing problems of off-line processing. Embodiments of the present invention provide a novel coagulant composition that eliminates off-line processing because no calcium carbonate is used, and, as a result, off-line chlorination, washing and siliconization are eliminated. The resulting process lowers the cost of production and yields a completely powder-free glove.